A=11
B=12
C=13
D=14
E=15
F=7
G=8
H=9
I=10
J=11
K=12
L=13
M=14
N=15
O=16
P=8
Q=9
R=10
S=11
T=12
U=13
V=14
W-Z seem to be slightly different. Working on it!
Not sure how they were derived yet, just noticed that:
P/Q = 8/9, and 128 is divisible by 8. The rest I worked out from there
Courtesy of f'' (last few and derivation)
W=15
X=16
Y=17
Z=9
Each is the sum of the digits in the decimal ASCII value for the capital letter